1. Field of the Invention
The present invention relates to an electronic control system and method for controlling a torque output of a vehicle drive in a manner that is less sensitive to accelerator pedal position when the vehicle drive is in a 4×4 mode of operation.
2. Description of Related Art
Motor vehicle internal combustion engines may be controlled using a torque control scheme where actual engine torque is controlled to a desired engine torque through an input adjusting device, such as with the electronic throttle, ignition timing, air-fuel ratio, or various other devices.
A torque-based electronic throttle (ETC) driver demand control system has been developed for use with all-wheel drive vehicles with manual and automatic transmissions. The ETC driver demand control system has employed a calibration table to provide a desired output torque in response to inputs to the table. For manual transmission applications, the inputs to the calibration table have been the engine speed and accelerator pedal position. For automatic transmission applications, the inputs to the calibration table have been the transmission output shaft speed and accelerator pedal position.
In manual transmission applications, the calibration table having inputs of engine speed and accelerator pedal position has been used to provide a wheel torque output in response to driver demand, regardless of whether the motor vehicle is operating in one of the normal drive gear modes or in a 4×4 low mode. In automatic transmission applications, the calibration table having inputs of transmission output shaft speed and accelerator pedal position has been used to provide a transmission output shaft torque in response to driver demand, regardless of whether the motor vehicle is operating in one of the normal drive gear modes or in a 4×4 low mode. Use of a calibration table in such a manner produces torque outputs that are distorted during operation of the vehicle drive in different modes as a result of the need to account for the 4×4 low mode of operation and also the normal drive gear modes of operation. For example, the wheel torque (manual transmission) or output shaft torque (automatic transmission) can be overly sensitive to accelerator pedal position when the vehicle drive is operated in the 4×4 low mode.
An object of the present invention is to provide an electronic control system and method for controlling a vehicle drive in a manner to overcome this problem of distortion and over-sensitivity of torque outputs to the position of the accelerator pedal when the vehicle drive is operated in a 4×4 mode.